Digital signals used in digital audio applications and similar applications are sampled at rates which are different in different systems. Therefore, in order to exchange data between the different systems, it is necessary to convert one sampling rate to another. An apparatus which converts one sampling rate to another while maintaining the waveforms of audio signals or the like in this way is known as a sampling rate converter.
When the output sampling timing is asynchronous with the input sampling timing, or when the ratio of the output sampling rate to the input sampling rate cannot be expressed in terms of a simple combination of integers, the ratio of the output sampling rate to the input sampling rate is accurately found, and then the sampling rate is converted to a different value, based on the accurately found ratio. In the prior art techniques, both the input sampling rate and the output sampling rate have been averaged in order to accurately find the sampling rate ratio.
In order to secure high accuracy, however, it is necessary to make the averaging time very long. Therefore, if the input and output sampling rates jitter at all, then the number of items of data calculated is not coincident with the number of items of data actually delivered. As a result, a malfunction occurs.